FIELD OF THE INVENTION

The present invention relates to raffinose synthetase genes and their use.

BACKGROUND OF THE INVENTION

Raffinose family oligosaccharides are derivatives of sucrose, which are represented by o-α-D-galactopyranosyl-(1→6) n-o-α-D-glucopyranosyl-(1→2)-β-D-fluctofuranoside as the general formula, and they are designated "raffinose" when n = 1, "stachyose" when n = 2, "verbascose" when n = 3, and "ajugose" when n = 4.

The greatest contents of such raffinose family oligosaccharides are found in plants, except for sucrose, and it has been known that they are contained not only in higher plants including gymnosperms such as pinaceous plants (e.g., spruce) and angiosperms such as leguminous plants (e.g., soybean, kidney bean), brassicaceous plants (e.g., rape), chenopodiaceous plants (e.g., sugar beet), malvaceous plants (e.g., cotton), and salicaceous plants (e.g., poplar), but also in green algae, chlorella. Thus, they occur widely in the plant kingdom similarly to sucrose.

Raffinose family oligosaccharides play a role as reserve sugars in the storage organs or seeds of many plants or as translocating sugars in the phenomenon of sugar transportation between the tissues of some plants.

Furthermore, it has been known that raffinose family oligosaccharides have an effect of giving good conditions of enterobacterial flora, if present at a suitable amount in food. Therefore, raffinose family oligosaccharides have already been used as a functional food material for addition to some kinds of food and utilized in the field of specified healthful food.

Raffinose family oligosaccharides having such a role and utility are produced by the raffinose oligosaccharide synthesis system beginning with sucrose in many plants. This biosynthesis system usually involves a reaction for the sequential addition of galactosyl groups from galactotinol through an α(1→6) bond to a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule.

In the first step of this biosynthesis system, raffinose synthetase is an enzyme concerned in the reaction of raffinose production by combining a D-galactosyl group from galactotinol through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule. It has been suggested that this enzyme constitutes a rate limiting step in the above synthesis system, and it has been revealed that this enzyme is quite important in the control of biosynthesis of raffinose family oligosaccharides.

The control of expression level or activity of raffinose synthetase in plants makes it possible to change the contents of raffinose family oligosaccharides in these plants. However, raffinose synthetase, although the presence of this enzyme itself was already confirmed in many plants by the measurement of its activity with a biochemical technique, has not yet been successfully isolated and purified as a homogeneous protein. In addition, the amino acid sequence of this enzyme is still unknown, and no report has been made on an attempt at beginning to isolate a gene coding for this enzyme.

SUMMARY OF THE INVENTION

Under these circumstances, the present inventors have intensively studied and finally succeeded in isolating a raffinose synthetase and a gene coding for this enzyme from broad bean, thereby completing the present invention.

Thus, the present invention provides the following:

• 1) A raffinose synthetase gene isolated from a plant and having a nucleotide sequence coding for an amino acid sequence of a protein capable of producing raffinose by combining a D-galactosyl group through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule.
• 2) The raffinose synthetase gene according to item 1, wherein the plant is a dicotyledon.
• 3) The raffinose synthetase gene according to item 2, wherein the dicotyledon is a leguminous plant.
• 4) The raffinose synthetase gene according to item 3, wherein the leguminous plant is broad bean.
• 5) A raffinose synthetase gene having a nucleotide sequence coding for protein (a) or (b) as defined below:

  • (a) protein having the amino acid sequence of SEQ ID NO:1;
  • (b) protein having an amino acid sequence derived by deletion, replacement, modification or addition of one or several amino acids in the amino acid sequence of SEQ ID NO:1, and capable of producing raffinose by combining a D-galactosyl group through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule.

• 6) A raffinose synthetase gene having the nucleotide sequence of SEQ ID NO:2.
• 7) The raffinose synthetase gene according to item 3, wherein the leguminous plant is soybean.
• 8) A raffinose synthetase gene having a nucleotide sequence coding for protein (a) or (b) as defined below:

  • (a) protein having the amino acid sequence of SEQ ID NO:3;
  • (b) protein having an amino acid sequence derived by deletion, replacement, modification or addition of one or several amino acids in the amino acid sequence of SEQ ID NO:3, and capable of producing raffinose by combining a D-galactosyl group through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule.

• 9) A raffinose synthetase gene having the nucleotide sequence of SEQ ID NO:4.
• 10) The raffinose synthetase gene according to item 2, wherein the dicotyledon is a lamiaceous plant.
• 11) The raffinose synthetase gene according to item 10, wherein the lamiaceous plant is Japanese artichoke.
• 12) A raffinose synthetase gene having a nucleotide sequence coding for the amino acid sequence of SEQ ID NO:5.
• 13) A raffinose synthetase gene having the nucleotide sequence of SEQ ID NO:6.
• 14) The raffinose synthetase gene according to item 1, wherein the plant is a monocotyledon.
• 15) The raffinose synthetase gene according to item 14, wherein the mono-cotyledon is a gramineous plant.
• 16) The raffinose synthetase gene according to item 15, wherein the gramineous plant is corn.
• 17) A raffinose synthetase gene having a nucleotide sequence coding for the amino acid sequence of SEQ ID NO:7.
• 18) A raffinose synthetase gene having the nucleotide sequence of SEQ ID NO:8.
• 19) A raffinose synthetase protein having amino acid sequence (a) or (b) as defined below:

  • (a) amino acid sequence of SEQ ID NO:1 or SEQ ID NO:3;
  • (b) amino acid sequence derived by deletion, replacement, modification or addition of one or several amino acids in the amino acid sequence of SEQ ID NO:1 or SEQ ID NO:3;
    
    

       the protein being capable of producing raffinose by combining a D-galactosyl group through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule.

• 20) A raffinose synthetase protein having the amino acid sequence of SEQ ID NO:1 or SEQ ID NO:3.
• 21) A gene fragment having a partial nucleotide sequence of the raffinose synthetase gene of item 1, 2, 3, 4, 7, 10, 11, 14, 15 or 16.
• 22) A gene fragment having a partial nucleotide sequence of the raffinose synthetase gene of item 5, 6, 8, 9, 12, 13, 17 or 18.
• 23) The gene fragment according to item 21 or 22, wherein the number of nucleotides is in the range of from 15 to 50.
• 24) A method for the detection of a raffinose synthetase gene or a gene fragment having a partial nucleotide sequence thereof, which comprises hybridizing a probe of the labeled gene fragment of item 21, 22 or 23 to an organism-derived genomic DNA or cDNA fragment; and detecting the DNA fragment bound specifically to the probe.
• 25) A method for the detection of a raffinose synthetase gene or a gene fragment having a partial nucleotide sequence thereof, which comprises hybridizing a probe of the labeled gene fragment of item 21, 22 or 23 to a plant-derived genomic DNA or cDNA fragment; and detecting the DNA fragment bound specifically to the probe.
• 26) A method for the amplification of a raffinose synthetase gene or a gene fragment having a partial nucleotide sequence thereof, which comprises annealing a primer having a nucleotide sequence of the gene fragment of item 21, 22 or 23 to organism-derived genomic DNA or cDNA; and amplifying the resulting DNA fragment by polymerase chain reaction.
• 27) A method for the amplification of a raffinose synthetase gene or a gene fragment having a partial nucleotide sequence thereof, which comprises annealing a primer having a nucleotide sequence of the gene fragment of item 21, 22 or 23 to plant-derived genomic DNA or cDNA; and amplifying the resulting DNA fragment by polymerase chain reaction.
• 28) A method for obtaining a raffinose synthetase gene, comprising the steps of identifying a DNA fragment containing a raffinose synthetase gene or a gene fragment having a partial nucleotide sequence thereof by the method of item 24, 25, 26 or 27; and isolating and purifying the DNA fragment identified.
• 29) A raffinose synthetase gene obtained by identifying a DNA fragment containing a raffinose synthetase gene or a gene fragment having a partial nucleotide sequence thereof by the method of item 24, 25, 26 or 27; and isolating and purifying the DNA fragment identified.
• 30) A chimera gene comprising the raffinose synthetase gene of item 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or 29, and a promoter linked thereto.
• 31) A transformant obtained by introducing the chimera gene of item 30 into a host organism.
• 32) A plasmid comprising the raffinose synthetase gene of item 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 29 or 30.
• 33) A host organism transformed with the plasmid of item 32, or a cell thereof.
• 34) A microorganism transformed with the plasmid of item 32.
• 35) A plant transformed with the plasmid of item 32, or a cell thereof.
• 36) A method for metabolic modification, which comprises introducing the raffinose synthetase gene of item 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 29 or 30 into a host organism or a cell thereof, so that the content of raffinose family oligosaccharides in the host organism or the cell thereof is changed.
• 37) A method for the production of a raffinose synthetase protein, which comprises isolating and purifying a raffinose synthetase protein from a culture obtained by cultivating the microorganism of item 34.
• 38) An anti-raffinose synthetase antibody capable of binding to the raffinose synthetase protein of item 19 or 20.
• 39) A method for the detection of a raffinose synthetase protein, which comprises treating a test protein with the anti-raffinose synthetase antibody of item 38; and detecting the raffinose synthetase protein by antigen-antibody reaction between the antibody and the raffinose synthetase protein.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the construction of plasmids used for the expression of a raffinose synthetase gene in Escherichia coli. pBluescriptKS-RS is a plasmid containing the raffinose synthetase gene cloned therein. RS represents the raffinose synthetase gene, and the nucleotide sequences shown in the upper portion of this figure are those of both terminal portions of the raffinose synthetase gene. A partial sequence represented by small letters is a nucleotide sequence derived from the vector pBluescriptII KS-. Two boxed nucleotide sequences are the initiation codon (ATG) and termination codon (TGATAA) of the raffinose synthetase gene, respectively. The recognition sites for several restriction endonucleases are shown above the nucleotide sequences. pGEX-RS and pTrc-RS are plasmids used for the expression of the raffinose synthetase gene in E. coli. Ptac, Ptrc, GST, lacI^q, and rrnB represent tac promoter, trc promoter, glutathione-S-transferase gene, lactose repressor gene, and termination signal for the transcription of ribosomal RNA, respectively.

Figure 2 shows the construction of expression vectors used for the expression in plants of chimera genes each having a raffinose synthetase gene and a promoter linked thereto. The restriction endonuclease map of the raffinose synthetase gene cloned in the plasmid pBluescriptKS-RS is shown in the lower portion of this figure. pBI221RS and pBI221(-)RS indicate the restriction endonuclease maps of expression vectors used for the transformation of soybean. 35S and NOS represent 35S promoter derived from cauliflower mosaic virus and nopaline synthetase gene terminator, respectively.

Figure 3 shows the construction of expression vectors used for the expression in plants of chimera genes each having a raffinose synthetase gene and a promoter linked thereto. The restriction endonuclease map of the raffinose synthetase gene cloned in the plasmid pBluescriptKS-RS is shown in the upper portion of this figure. pBI121RS and pBI121(-)RS indicate the restriction endonuclease maps of binary vectors used for the transformation of mustard. For the binary vector, only a region between the right border and the left border is shown. 35S, NOS and NPT represent 35S promoter derived from cauliflower mosaic virus, nopaline synthetase gene terminator and kanamycin resistance gene, respectively.

DETAILED DESCRIPTION OF THE INVENTION

The gene engineering methods described below can be carried out according to ordinary methods, for example, as described in "Molecular Cloning: A Laboratory Manual 2nd edition" (1989), Cold Spring Harbor Laboratory Press, ISBN 0-87969-309-6; "Current Protocols In Molecular Biology" (1987), John Wiley & Sons, Inc. ISBN 0-471-50338-X; and "Current Protocols In Protein Science" (1995), John Wiley & Sons, Inc. ISBN 0-471-11184-8.

The term "raffinose synthetase gene" as used herein refers to a gene having a nucleotide sequence coding for the amino acid sequence of a protein capable of producing raffinose by combining a D-galactosyl group through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule (hereinafter referred to simply as the present gene), and such a gene can be prepared, for example, from plants.

More specifically, the present gene can be prepared from dicotyledons such as leguminous plants (e.g., broad bean, soybean) and lamiaceous plants (e.g., Japanese artichoke) or from monocotyledons such as gramineous plants (e.g., corn). Specific examples of the present gene are a "raffinose synthetase gene having a nucleotide sequence coding for a protein having the amino acid sequence of SEQ ID NO:1"; a "raffinose synthetase gene having a nucleotide sequence coding for a protein having an amino acid sequence derived by deletion, replacement, modification or addition of one or several amino acids in the amino acid sequence of SEQ ID NO:1, and capable of producing raffinose by combining a D-galactosyl group through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule"; a "raffinose synthetase gene having a nucleotide sequence coding for a protein having the amino acid sequence of SEQ ID NO:3"; a "raffinose synthetase gene having a nucleotide sequence coding for a protein having an amino acid sequence derived by deletion, replacement, modification or addition of one or several amino acids in the amino acid sequence of SEQ ID NO:3, and capable of producing raffinose by combining a D-galactosyl group through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule"; a "raffinose synthetase gene having a nucleotide sequence coding for the amino acid sequence of SEQ ID NO:5"; and a "raffinose synthetase gene having a nucleotide sequence coding for the amino acid sequence of SEQ ID NO:7."

In a further embodiment, the invention relates to nucleic acid molecules of at least 15 nucleotides in length hybridizing specifically with a nucleic acid molecule as described above or with a complementary strand thereof. Specific hybridization occurs preferably under stringent conditions and implies no or very little cross-hybridization with nucleotide sequences encoding no or substantially different (oligo)peptides. Such nucleic acid molecules may be used as probes and/or for the control of gene expression. Nucleic acid probe technology is well known to those skilled in the art who will readily appreciate that such probes may vary in length. Preferred are nucleic acid probes of 17 to 50, particularly preferred 21 to 50 nucleotides in length. Of course, it may also be appropriate to use nucleic acids of up to 100 and more nucleotides in length. The nucleic acid probes of the invention are useful for various applications. On the one hand, they may be used as PCR primers for amplification of regulatory sequences according to the invention. Another application is the use as a hybridization probe to identify nucleic acid molecules hybridizing with a nucleic acid molecule of the invention by homology screening of genomic DNA libraries. Nucleic acid molecules according to this preferred embodiment of the invention which are complementary to a nucleic acid molecule as described above may also be used for repression of expression of a gene comprising such regulatory sequences, for example due to an antisense or triple helix effect or for the construction of appropriate ribozymes (see, e.g., EP-B1 0 291 533, EP-A1 0 321 201, EP-A2 0 360 257) which specifically cleave the (pre)-mRNA of a gene comprising a nucleic acid molecule of the invention. Selection of appropriate target sites and corresponding ribozymes can be done as described for example in Steinecke, Ribozymes, Methods in Cell Biology 50, Galbraith et al. eds Academic Press, Inc. (1995), 449-460. Furthermore, the person skilled in the art is well aware that it is also possible to label such a nucleic acid probe with an appropriate marker for specific applications, such as for the detection of the presence of a nucleic acid molecule of the invention in a sample derived from an organism.

The above described nucleic acid molecules may either be DNA or RNA or a hybrid thereof. Furthermore, said nucleic acid molecule may contain, for example, thioester bonds and/or nucleotide analogues, commonly used in oligonucleotide anti-sense approaches. Said modifications may be useful for the stabilization of the nucleic acid molecule against endo- and/or exonucleases in the cell. Said nucleic acid molecules may be transcribed by an appropriate vector containing a chimeric gene which allows for the transcription of said nucleic acid molecule in the cell. Such nucleic acid molecules may further contain ribozyme sequences which specifically cleave the (pre)-mRNA comprising the nucleic acid molecule of the invention. Furthermore, oligonucleotides can be designed which are complementary to a nucleic acid molecule of the invention (triple helix; see Lee, Nucl. Acids Res. 6 (1979), 3073; Cooney, Science 241 (1988), 456 and Dervan, Science 251 (1991), 1360), thereby preventing transcription and the production of the encoded oligopeptide.

The present gene can be obtained, for example, by the following method.

The tissues of a leguminous plant such as broad bean (Vicia faba) or soybean (Glycine max) are frozen in liquid nitrogen and ground physically with a mortar or other means into finely powdered tissue debris. From the tissue debris, RNA is extracted by an ordinary method. Commercially available RNA extraction kits can be utilized in the extraction. The whole RNA is separated from the RNA extract by ethanol precipitation. From the whole RNA separated, poly-A tailed RNA is fractionated by an ordinary method. Commercially available oligo-dT columns can be utilized in the fractionation. cDNA is synthesized from the fraction obtained (i.e., poly-A tailed RNA) by an ordinary method. Commercially available cDNA synthesis kits can be utilized in the synthesis.

For example, cDNA fragments of the "raffinose synthetase gene having a nucleotide sequence coding for a protein having the amino acid sequence of SEQ ID NO:1" as the present gene can be obtained by PCR amplification using the broad bean-derived cDNA obtained above as a template and primers 1 to 3 shown in list 1 below. The primers used therein can be designed and synthesized on the basis of the nucleotide sequence of SEQ ID NO:2, depending upon the purpose. For example, in order to amplify the open reading frame region of the "raffinose synthetase gene having a nucleotide sequence coding for a protein having the amino acid sequence of SEQ ID NO:1," primers 1 to 4 shown in list 2 below may be designed and synthesized.

In the same manner, cDNA fragments of the "raffinose synthetase gene having a nucleotide sequence coding for a protein having the amino acid sequence of SEQ ID NO:3" can be obtained by PCR amplification with the soybean-derived cDNA obtained above as a template and, for example, primers 4 to 6 shown in list 1 below. The primers used therein can be designed and synthesized on the basis of the nucleotide sequence of SEQ ID NO:4, depending upon the purpose. For example, in order to amplify the open reading frame region of the "raffinose synthetase gene having a nucleotide sequence coding for a protein having the amino acid sequence of SEQ ID NO:3," primers 5 to 8 shown in list 2 below may be designed and synthesized.

The amplified DNA fragments can be subcloned according to ordinary methods, for example, as described in "Molecular Cloning: A Laboratory Manual 2nd edition" (1989), Cold Spring Harbor Laboratory Press; and "Current Protocols In Molecular Biology" (1987), John Wiley & Sons, Inc. ISBN 0-471-50338-X. More specifically, cloning can be effected, for example, using a TA cloning kit (Invitrogen) and a plasmid vector such as pBluescript II (Stratagene). The nucleotide sequences of the DNA fragments cloned can be determined by the dideoxy terminating method, for example, as described by F. Sanger, S. Nicklen, A.R. Coulson, Proceedings of National Academy of Science U.S.A. (1977), 74, pp. 5463-5467. For example, ABI PRISM Dye Terminator Cycle Sequencing Ready Reaction Kit commercially available from Perkin-Elmer may preferably be used.

(List 1)

Primer 1:

AATTTTCAAG CATAGCCAAG TTAACCACCT 30 mer

Primer 2:

GCTCACAAGA TAATGATGTT AGTC 24 mer

Primer 3:

ATACAAGTGA GGAACTTGAC CA 22 mer

Primer 4:

CCAAACCATA GCAAACCTAA GCAC 24 mer

Primer 5:

ACAACAGAAA AATATGACTC TTATTACT 28 mer

Primer 6:

AAAAGAGAGT CAAACATCAT AGTATC 26 mer

(List 2)

Primer 1:

ATGGCACCAC CAAGCATAAC CAAAACTGC 29 mer

Primer 2:

ATGGCACCAC CAAGCATAAC CAAAACTGCA ACCCTCCAAG ACG 43 mer

Primer 3:

TCAAAATAAA AACTGGACCA AAGAC 25 mer

Primer 4:

TCAAAATAAA AACTGGACCA AAGACAATGT 30 mer

Primer 5:

ATGGCTCCAA GCATAAGCAA AACTG 25 mer

Primer 6:

ATGGCTCCAA GCATAAGCAA AACTGTGGAA CT 32 mer

Primer 7:

TCAAAATAAA AACTCAACCA TTGAC 25 mer

Primer 8:

TCAAAATAAA AACTCAACCA TTGACAATTT TGAAGCACT 39 mer

The term "gene fragment" as used herein refers to a gene fragment having a partial nucleotide sequence of the present gene (hereinafter referred to simply as the present gene fragment). For example, it may be a gene fragment derived from a plant and having a partial nucleotide sequence of the gene having a nucleotide sequence coding for a protein capable of producing raffinose by combining a D-galactosyl group through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule. Specific examples of the present gene fragment are a gene fragment having a partial nucleotide sequence of the gene having a nucleotide sequence coding for the amino acid sequence of SEQ ID NO:1 and a gene fragment having a partial nucleotide sequence of the gene having a nucleotide sequence of SEQ ID NO:2, more specifically a gene fragment having a nucleotide sequence or a partial nucleotide sequence thereof, coding for any of the amino acid sequences shown in list 3 below.

These gene fragments can be used as probes in the hybridization method or as primers in the PCR method. For the primers in the PCR method, it is generally preferred that the number of nucleotides is greater from a viewpoint that the specificity of annealing is ensured; it is, however, also preferred that the number of nucleotides is not so great from viewpoints that the primers themselves are liable to have a higher structure giving possible deterioration of the annealing efficiency and that complicated procedures are required in the purification after the synthesis. In usual cases, preferred is a gene fragment consisting of single-stranded DNA, wherein the number of nucleotides is in the range of from 15 to 50.

(List 3)

#1

Gly Ile Lys Phe Met Ser Ile Phe Arg Phe Lys Val Trp Trp Thr Thr His Trp Val Gly

#2

Ile Ile Asp Lys Phe Gly Trp Cys Thr Trp Asp Ala Phe Tyr

#3

Gly Gly Cys Pro Pro Gly Phe Val Ile Ile Asp Asp Gly Trp Gln

#4

Thr Ser Ala Gly Glu Gln Met Pro Cys Arg Leu Val Lys Tyr Glu Glu Asn

#5

Val Tyr Val Trp His Ala Leu Cys Gly Tyr Trp Gly Gly Val Arg Pro

#6

Thr Met Glu Asp Leu Ala Val Asp Lys Ile Val Glu Asn Gly Val Gly Leu Val Pro Pro

#7

Gly Leu His Ser His Leu Glu Ser Ala Gly Ile Asp Gly Val Lys Val Asp Val Ile His Leu Leu Glu

#8

Gly Gly Arg Val Glu Leu Ala Arg Ala Tyr Tyr Lys Ala Leu

#9

Val Lys Lys His Phe Lys Gly Asn Gly Val Ile Ala

#10

Glu His Cys Asn Asp Phe Phe Leu Leu Gly Thr Glu Ala Ile Ser Leu Gly Arg Val Gly Asp Asp Phe Trp Cys Ser Asp Pro Ser Gly Asp Pro Asn Gly Thr Tyr Trp Leu Gln Gly Cys His Met Val His Cys

#11

Ala Tyr Asn Ser Leu Trp Met Gly Asn Phe Ile Gln Pro Asp Trp Asp Met Phe Gln Ser Thr His Pro Cys Ala Glu Phe His Ala Ala Ser Arg Ala Ile Ser Gly Gly Pro Ile Tyr Val Ser Asp

#12

Leu Pro Asp Gly Ser Ile Leu Arg Cys

#13

Ala Leu Pro Thr Arg Asp Cys Leu Phe Glu Asp Pro Leu His Asn Gly Lys Thr Met Leu Lys Ile Trp Asn

#14

Gly Val Leu Gly Leu Phe Asn Cys Gln Gly Gly Gly Trp

#15

Phe Ala Pro Ile Gly Leu Val Asn Met

The present gene fragment is labeled, and then used as a probe in the hybridization method and hybridized to organism-derived DNA, so that a DNA fragment having the probe specifically bound thereto can be detected. Thus, from an organism-derived gene library, a raffinose synthetase gene having a nucleotide sequence coding for the amino acid sequence of an enzyme capable of producing raffinose by combining a D-galactosyl group through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule; or a gene fragment having a partial nucleotide sequence thereof, can be detected (hereinafter referred to simply as the present detection method).

As the organism-derived DNA, for example, a cDNA library or a genomic DNA library of a desired plant can be used. The gene library may also be a commercially available gene library as such or a library prepared according to an ordinary library preparation method, for example, as described in "Molecular Cloning: A Laboratory Manual 2nd edition" (1989), Cold Spring Harbor Laboratory Press; "Current Protocols In Molecular Biology" (1987), John Wiley & Sons, Inc. ISBN 0-471-50338-X.

As the hybridization method, plaque hybridization or colony hybridization can be employed, depending upon the kind of vector used in the preparation of a library. More specifically, when a library to be used is constructed with a phage vector, a suitable host microorganism is mixed with the phage under infectible conditions, which is further mixed with a soft agar medium, and the mixture is plated on an agar medium. Thereafter, a culture is grown at 37°C until a plaque of an appropriate size appears. When a library to be used is constructed with a plasmid vector, the plasmid is transformed in a suitable host microorganism to form a transformant. The transformant obtained is diluted to a suitable concentration, and the dilution is plated on an agar medium, after which a culture is grown at 37°C until a colony of an appropriate size appears.

In either case of the above libraries, a membrane filter is placed on the surface of the agar medium after the cultivation, so that the phage or transformant is transferred to the membrane. This membrane is denatured with an alkali, followed by neutralization, and for example, when a nylon membrane is used, the membrane is irradiated with ultraviolet light, so that DNA is fixed on the membrane. This membrane is then subjected to hybridization with the present gene fragment labeled by an ordinary method as a probe. For this method, reference may be made, for example, to D.M. Glover ed., "DNA cloning, a practical approach" IRL PRESS (1985), ISBN 0-947946-18-7. There are various reagents and temperature conditions to be used in the hybridization; for example, prehybridization is carried out by the addition of 6 x SSC (0.9 M NaCl, 0.09 M citric acid), 0.1-1% SDS, 100 µg/ml denatured salmon sperm DNA, and incubation at 65°C for 1 hour. The present gene fragment labeled is then added as a probe, and mixed. Hybridization is carried out at 42-68°C for 4 to 16 hours. The membrane is washed with 2 x SSC, 0.1-1% SDS, further rinsed with 0.2 x SSC, 0-0.1% SDS, and then dried. The membrane is analyzed, for example, by autoradiography or other techniques, to detect the position of the probe on the membrane and thereby detect the position of DNA having a nucleotide sequence homologous to that of the probe used Thus, the present gene or the present gene fragment can be detected. The clone corresponding to the position of DNA thus detected on the membrane is identified on the original agar medium, and the positive clone is selected, so that the clone having the DNA can be isolated. The same procedures of detection are repeated to purify the clone having the DNA.

Other detection methods can also be used, for example, GENE TRAPPER cDNA Positive Selection System Kit commercially available from Gibco BRL. In this method, a single-stranded DNA library is hybridized with the present gene fragment biotinylated (i.e., probe), followed by the addition of streptoavidin-bound magnet beads and mixing. From the mixture, the streptoavidin-bound magnetic beads are collected with a magnet, so that single-stranded DNA having a nucleotide sequence homologous to that of the probe used, which has been bound to these beads through the present gene fragment, biotin and streptoavidin, is collected and detected. Thus, the present gene or the present gene fragment can be detected. The single-stranded DNA collected can be changed into a double-strand form by treatment with a suitable DNA polymerase using a suitable oligonucleotide as a primer.

The present detection method may also be used in the analysis of a plant. More specifically, plant genomic DNA is prepared according to an ordinary method, for example, as described in "Cloning and Sequence (Plant Biotechnology Experiment Manual)" complied under the supervision of Itaru Watanabe, edited by Masahiro Sugiura, published by Noson Bunka-sha, Tokyo (1989). The plant genomic DNA is digested with several kinds of suitable restriction endonucleases, followed by electrophoresis, and the electrophoresed DNA is blotted on a filter according to an ordinary method. This filter is subjected to hybridization with a probe prepared from the present gene fragment by an ordinary method, and DNA fragments to which the probe hybridizes are detected. The DNA fragments detected are compared in length between different varieties of a specified plant species. The differences in length make possible the analysis of differences in phenotypic characteristics accompanied with the expression of raffinose family oligosaccharides between these varieties. Furthermore, when the DNA fragments detected by the above method are compared in length between the gene recombinant plant and the non-gene recombinant plant of the same variety, the former plant can be discriminated from the latter plant by the detection of hybridizing bands greater in number or higher in concentration for the former plant than for the latter plant. This method can be carried out according to the RFLP (restriction fragment length polymorphism) method, for example, as described in "Plant PCR Experiment Protocols" complied under the supervision of Ko Shimamoto and Takuji Sasaki, published by Shujun-sha, Tokyo (1995), ISBN 4-87962-144-7, pp. 90-94.

The PCR method using a primer having the nucleotide sequence of the present gene fragment makes it possible to amplify from organism-derived DNA, a raffinose synthetase gene having a nucleotide sequence coding for the amino acid sequence of an enzyme capable of producing raffinose by combining a D-galactosyl group through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule; or a gene fragment having a partial nucleotide sequence thereof (hereinafter referred to simply as the present amplification method).

More specifically, for example, an oligonucleotide having 15 to 50 nucleotides in the nucleotide sequence of the present gene fragment at the 3'-terminus is chemically synthesized by an ordinary synthesis method. Based on the codon table below, showing the correspondence of amino acids encoded in nucleotide sequences, a mixed primer can also be synthesized so that a residue at a specified position in the primer is changed to a mixture of several bases, depending upon the variation of codons which can encode a certain amino acid.

CODON TABLE

Phe

UUU

Ser

UCU

Tyr

UAU

Cys

UGU

UUC

UCC

UAC

UGC

Leu

UUA

UCA

Stop

UAA

Stop

UGA

UUG

UCG

UAG

Trp

UGG

CUU

Pro

CCU

His

CAU

Arg

CGU

CUC

CCC

CAC

CGC

CUA

CCA

Gln

CAA

CGA

CUG

CCG

CAG

CGG

Ile

AUU

Thr

ACU

Asn

AAU

Ser

AGU

AUC

ACC

AAC

AGC

AUA

ACA

Lys

AAA

Arg

AGA

Met

AUG

ACG

AAG

AGG

Val

GUU

Ala

GCU

Asp

GAU

Gly

GGU

GUC

GCC

GAC

GGC

GUA

GCA

Glu

GAA

GGA

GUG

GCG

GAG

GGG

Furthermore, a base capable of forming a pair with plural kinds of bases, such as inosine, can also be used instead of the above mixture of several bases. More specifically, for example, primers having nucleotide sequences as shown in list 4 can be used. In this context, an oligonucleotide having the same nucleotide sequence as the coding strand of the present gene consisting of double-stranded DNA is designated "sense primer," and an oligonucleotide having a nucleotide sequence complementary to the coding strand, "antisense primer."

A sense primer having the same nucleotide sequence as present on the 5'-upstream side in the coding strand of a raffinose synthetase gene or a gene fragment having a partial nucleotide sequence thereof to be amplified, and an antisense primer having a nucleotide sequence complementary to the nucleotide sequence on the 3'-downstream side in this coding strand, are used in combination for PCR reaction to amplify a DNA fragment, for example, with a gene library, genomic DNA or cDNA as a template. At this time, the amplification of a DNA fragment can be confirmed by an ordinary method with electrophoresis. For the DNA fragment amplified, its restriction endonuclease map is constructed or its nucleotide sequence is determined by an ordinary method, so that the present gene or the present gene fragment can be identified. As the gene library used herein, for example, a cDNA library or a genomic cDNA library of a desired plant can be used. For the plant gene library, a commercially available library derived from plant can be used as such; or a library prepared according to an ordinary library preparation method, for example, as described in "Molecular Cloning: A Laboratory Manual 2nd edition" (1989), Cold Spring Harbor laboratory Press or "Current Protocols in Molecular Biology" (1987), John Wiley & Sons, Inc., ISBN 0-471-50338-X, can also be used. As the genomic DNA or cDNA used in the present amplification method, for example, cDNA or genomic cDNA prepared from a desired plant can be used.

More specifically, for example, a primer designed on the amino acid sequence of SEQ ID NO:1 is used for the present amplification method with cDNA derived from Japanese artichoke, which is a lamiaceous plant, as a template, so that a raffinose synthetase gene fragment having the nucleotide sequence of SEQ ID NO:6 can be amplified. Furthermore, for example, a primer designed on the amino acid sequence of SEQ ID NO:1 is used for the present amplification method with cDNA derived from corn, which is a gramineous plant, as a template, so that a raffinose synthetase gene fragment having the nucleotide sequence of SEQ ID NO:8 can be amplified.

(List 4)

1-F

32mer

TTIAAIGTITGGTGGACIACICAITGGGTIGG

2-F

41mer

ATIATIGAIAAITTIGGITGGTGIACITGGGAIGCITTITA

2-RV

41mer

TAIAAIGCITCCCAIGTICACCAICCIAAITTITCIATIAT

3-F

44mer

GGIGGITGICCICCIGGITTIGTIATIATIGAIGAIGGITGGCA

3-RV

44mer

TGCCAICCITCITCIATIATIACIAAICCIGGIGGICAICCICC

4-F

32mer

AAIAAICAITTIAAIGGIAAIGGIGTIATIGC

4-RV

32mer

GCIATIACICCITTICCITTIAAITGITTITT

5-F

38mer

TGGATGGGIAAITTIATICAICCIGAITGGGAIATGTT

5-RV

38mer

AACATITCCCAITCIGGITGIATIAAITTICCCATCCA

6-RV

27mer

CATITTIACIA(AG)ICCIATIGGIGCIAA

The present amplification method can also be utilized for the analysis of a plant gene. More specifically, for example, plant genomic DNA prepared from different vaneties of a specified plant species is used as a template for the present amplification method to amplify a DNA fragment. The DNA fragment amplified is mixed with a solution of formaldehyde, which is denatured by heating at 85°C for 5 minutes, followed by rapid cooling on ice. This sample is subjected to electrophoresis, for example, on a 6% polyacrylamide gel containing 0% or 10% glycerol. In this electrophoresis, a commercially available electrophoresis apparatus for SSCP (single strand conformation polymorphism) can be used, and electrophoresis is carried out, while the gel is kept at a constant temperature, e.g., 5°C, 25°C or 37°C. From the electrophoresed gel, a DNA fragment is detected, for example, by a method such as silver staining method with commercially available reagents.

From the differences of behavior between the varieties in the electrophoresis of the DNA fragment detected, a mutation in the raffinose synthetase gene is detected, and an analysis is carried out for differences caused by the mutation in phenotypic characteristics accompanied with the expression of raffinose family oligosaccharides. This method can be carried out according to the SSCP method, for example, as described in "Plant PCR Experiment Protocols" complied under the supervision of Ko Shimamoto and Takuji Sasaki, published by Shujun-sha, Tokyo (1995), ISBN 4-87962-144-7, pp. 141-146.

The present detection method or the present amplification method as described above can also be used for identifying a raffinose synthetase gene or a gene fragment having a partial nucleotide sequence thereof and then isolating and purifying the identified gene or gene fragment thereof to obtain the present gene (hereinafter referred to simply as the present gene acquisition method).

The present gene or the present gene fragment can be obtained, for example, by detecting a probe consisting of the present gene fragment hybridized to DNA in the organism-derived gene library by the present detection method as described above to identify DNA having a nucleotide sequence homologous with the probe used; purifying a clone carrying the DNA; and isolating and purifying plasmid or phage DNA from the clone. When the DNA thus obtained is a gene fragment having a partial nucleotide sequence of the raffinose synthetase gene, further screening of the gene library by the present gene detection method using the DNA as a probe gives the present gene in full length.

The present gene or the present gene fragment can be identified, for example, by effecting polymerase chain reaction using a primer having the nucleotide sequence of the present gene fragment to amplify a DNA fragment from the organism-derived DNA by the present amplification method as described above; and then constructing a restriction endonuclease map or determining a nucleotide sequence for the amplified DNA fragment. Based on the nucleotide sequence of the gene fragment obtained, an antisense primer is synthesized for the analysis of 5'-terminal sequences, and a sense primer is synthesized for the analysis of 3'-terminal sequences. The nucleotide sequence of the present gene in full length can be determined by the RACE method using these primers and a commercially available kit, e.g., Marathon Kit of Clontech. The present gene in full length can be obtained by synthesizing new primers based on both terminal sequences in the nucleotide sequence thus determined and effecting polymerase chain reaction again.

The present gene acquisition method as described above makes it possible to obtain raffinose synthetase genes as the present gene from various organisms. For example, a gene coding for a raffinose synthetase having an amino acid sequence that has about 50% or higher homology, in the region corresponding to the length of 400 or more amino acids, with the amino acid sequence of SEQ ID NO:1, and capable of producing raffinose by combining a D-galactosyl group through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule. More specifically, for example, a raffinose synthetase gene having the nucleotide sequence of SEQ ID NO:4 can be obtained by amplifying and identifying a DNA fragment containing a gene fragment having a partial nucleotide sequence of the raffinose synthetase gene by the present amplification method using primers designed from the amino acid sequence of SEQ ID NO:1 and soybean cDNA as a template; isolating and purifying the identified DNA fragment, followed by the above procedures to obtain a full-length gene containing the DNA fragment.

A chimera gene comprising the present gene and a promoter linked thereto (hereinafter referred to simply as the present chimera gene) can be constructed.

The promoter to be used is not particularly limited, so long as it is functionable in a host organism to be transformed. The promoter may include, for example, synthetic promoters functionable in Escherichia coli, such as E. coli lactose operon promoter, E. coli tryptophan operon promoter and tac promoter; yeast alcohol dehydrogenase gene (ADH) promoter, adenovirus major late (Ad.ML) promoter, SV40 early promoter, and baculovirus promoter.

When the host organism is a plant or a cell thereof, the promoter may include, for example, T-DNA derived constitutive promoters such as nopaline synthetase gene (NOS) promoter and octopine synthase gene (OCS) promoter; plant virus-derived promoters such as cauliflower mosaic virus (CaMV) derived 19S and 35S promoter; derived promoters such as phenylalanine ammonia-lyase (PAL) gene promoter, chalcone synthetase (CHS) gene promoter and pathogenesis-related protein (PR) gene promoter. Furthermore, vector pSUM-GY1 (see JP-A 06-189777/1994) can also be used, which has a promoter giving specific expression in a specified plant tissue, e.g., a promoter of soybean-derived seed storage protein glycinin gene. The use of a chimera gene constructed so as to have such a promoter makes it possible to increase or decrease the content of raffinose family oligosaccharides in a specified tissue of a plant.

The present chimera gene is then introduced into a host organism according to an ordinary gene engineering method to give a transformant. If necessary, the present chimera gene may be used in the form of a plasmid, depending upon the transformation method for introducing the gene into the host organism. Furthermore, the present chimera gene may contain a terminator. In this case, it is generally preferred that the chimera gene is constructed so as to have a terminator downstream the raffinose synthetase gene. The terminator to be used is not particularly limited, so long as it is functionable in a host organism to be transformed. For example, when the host organism is a plant or a cell thereof, the terminator may include, for example, T-DNA derived constitutive terminators such as nopaline synthetase gene (NOS) terminator; and plant derived terminators such as terminators of allium virus GV1 or GV2.

If necessary, the present gene may be used in the form of a plasmid. For example, when the host organism is a microorganism, the plasmid constructed is introduced into the microorganism by an ordinary means, for example, as described in "Molecular Cloning: A Laboratory Manual 2nd edition" (1989), Cold Spring Harbor laboratory Press or "Current Protocols in Molecular Biology" (1987), John Wiley & Sons, Inc., ISBN 0-471-50338-X. The microorganism thus transformed is selected with a marker such as antibiotic resistance or auxotrophy. When the host organism is a plant, the plasmid constructed is introduced into a plant cell by an ordinary means such as infection with Agrobacterium (see JP-B 2-58917/1990 and JP-A 60-70080/1985), electroporation into protoplasts (see JP-A 60-251887/1985 and JP-B 5-68575/1993) or particle gun method (see JP-A 5-508316/1993 and JP-A 63-258525/1988). The plant cell transformed by the introduction of a plasmid is selected with an antibiotic such as kanamycin or hygromycin. From the plant cell thus transformed, a transformed plant can be regenerated by an ordinary plant cell cultivation method, for example, as described in "Plant Gene Manipulation Manual (How to Produce Transgenic Plants)" written by Uchimiya, 1990, Kodan-sha Scientific (ISBN 4-06-153513-7), pp. 27-55. Furthermore, the collection of seeds from the transformed plant also makes it possible to prolify the transformed plant. In addition, crossing between the transformed plant obtained and the non-transformed plant makes it possible to produce progenic plants with the character of the transformed plant.

The content of raffinose family oligosaccharides can be changed by introducing the present gene into a host organism or a cell thereof, and modifying the metabolism in the host organism or the cell thereof. As such a method, for example, there can be used a method for metabolic modification to increase the amount of raffinose family oligosaccharides in a host organism or a cell thereof by constructing the present chimera gene comprising the present gene and a promoter linked thereto, in which case the present gene is linked to the promoter in an original direction suitable for transcription, translation, and expression as a protein, and then introducing the present chimera gene into the host organism or the cell thereof; or a method for metabolic modification to decrease the amount of raffinose family oligosaccharides in a host organism or a cell thereof by constructing the present chimera gene comprising the present gene and a promoter linked thereto, in which case the present gene is linked to a promoter in a reverse direction unsuitable for translation and expression as a protein, and then introducing the present chimera gene into the host organism or the cell thereof.

The term "raffinose synthetase protein" as used herein refers to a protein encoded in the present gene (hereinafter referred to simply to the present protein). For example, it may include an enzyme protein having the amino acid sequence of SEQ ID NO:1 or SEQ ID NO: 3, or having an amino acid sequence derived by deletion, replacement, modification or addition of one or several amino acids in the amino acid sequence of SEQ ID NO:1 or SEQ ID NO:3; and capable of producing raffinose by combining a D-galactosyl group through an α(1→6) bond with a hydroxyl group attached to the carbon atom at position 6 of a D-glucose residue in a sucrose molecule.

Specific examples of the present protein are an enzyme protein having the amino acid sequence of SEQ ID NO:1 (799 amino acids; molecular weight, 89 kDa) and an enzyme protein having the amino acid of SEQ ID NO:3 (781 amino acids; molecular weight, 87 kDa).

The present protein, although it can be prepared, for example, from leguminous plants such as broad bean (Vicia faba), by an ordinary biochemical method such as (NH₄)₂SO₄ precipitation, ion exchange column, hydrophobic column, hydroxyapatite column or gel filtration column, can also be prepared from the host organism transformed with the present plasmid, or a cell thereof. More specifically; for example, using GST Gene Fusion Vectors Kit of Pharmacia, the present gene is inserted into an expression vector plasmid attached to the Kit. The resulting vector plasmid is introduced into a microorganism such as E. coli according to an ordinary gene engineering method. A culture of the transformant obtained is grown on a medium with the addition of IPTG (isopropylthio-β-D-galactoside), so that the present protein can be expressed and derived as a fused protein in the culture. The fused protein expressed and induced can be isolated and purified by an ordinary method such as disruption of bacterial cells, column operation or SDS-PAGE electrophoresis. The digestion of the fused protein with a protease such as thrombin or blood coagulation factor Xa gives the present protein. This may preferably be made, for example, according to the method described in "Current Protocols In Protein Science" (1995), John Wiley & Sons, Inc. ISBN 0-471-11184-8. The activity of the present protein can be measured, for example, by the method described in L. Lehle and W. Tanner, Eur. J. Biochem., 38, 103-110 (1973).

An anti-raffinose synthetase antibody capable of binding to a raffinose synthetase protein (hereinafter referred to simply as the present antibody) can be produced by an ordinary immunological method using the present protein prepared above, as an antigen. More specifically, the present antibody can be produced, for example, according to the method described in Ed Harlow and David Lane, "Antibodies: A Laboratory Manual" (1988), Cold Spring Harbor Laboratory Press, ISBN 0-87969-314-2.

The present protein can be detected by treating test proteins with the present antibody and detecting a protein having the present antibody bound specifically thereto. Such a detection method can be carried out according to an immunological technique such as Western blot method or enzyme-linked immunosorbent assay (ELISA), for example, as described in Ed Harlow and David Lane, "Antibodies: A Laboratory Manual" (1988), Cold Spring Harbor Laboratory Press.

The Western blot method is carried out, for example, as follows: Proteins are extracted from a plant, for example, according to the method described in Methods in Enzymology, volume 182, "Guide to Protein Purification," pp. 174-193, ISBN 9-12-182083-1. The composition of an extraction buffer can suitably be changed depending upon the plant tissue used. The proteins extracted are electrophoresed according to an ordinary SDS-PAGE method. The proteins electrophoresed in the gel are transferred to a membrane by Western blotting with an ordinary electrical method. More specifically, for example, the gel is immersed in a transfer buffer (25 mM Tris, 192 mM glycine, 20% methanol) for 10 minutes, and then placed onto a PVDF membrane cut into the same size as that of the gel. The gel together with the membrane is set in a commercially available transfer apparatus of the semi-dry type. Blotting is carried out at a constant current of 0.8 to 2 mA/cm² for 45 minutes to 1 hour. The proteins transferred to the membrane can be detected immunologically with a kit for Western blot detection using a primary antibody, and a secondary antibody or protein A, which has been labeled with alkaline phosphatase or horseradish peroxidase. At this time, the present protein on the membrane call be detected by the use of the present antibody as a primary antibody.

In the ELISA method, for example, the property of proteins binding to the surface of a 96-well ELISA plate made of a resin is utilized in principle for the immunological detection of an antigen finally bound to the surface of the ELISA plate. The test proteins are added as a solution and bound to an ELISA plate, followed by blocking, for example, by the addition of PBS containing a protein such as 5% bovine serum albumin. Thereafter, the well is washed with PBS, to which a solution containing the present antibody is added to effect the reaction. After the well is washed, a solution containing a secondary antibody labeled with alkaline phosphatase or horseradish peroxidase is further added to the well, followed by washing. Finally, a substrate solution for detection is added to the well, and the color development of the substrate is detected with an ELISA reader.

In another method, the present antibody is added and bound to an ELISA plate, followed by blocking, for example, by the addition of PBS containing a protein such as 5% bovine serum albumin. The test proteins are then added as a solution, and an antigen contained in the test proteins is bound to the present antibody that has been bound to the plate, followed by washing, and the present antibody is further added to the well. The present antibody used at this time is preferably one prepared from an animal species different from that used for the preparation of the present antibody used first. A solution containing a secondary antibody labeled with alkaline phosphatase or horseradish peroxidase is then added to the well, followed by washing. The secondary antibody used at this time must have the property of binding to the present antibody added later. Finally, a substrate solution for detection is added, and the color development is detected with an ELISA reader.

Examples

The present invention will be further illustrated by the following examples; however, the present invention is not limited to these example in any way whatsoever.

Example 1 (Purification of Galactinol)

About 250 ml of sugar beet blackstrap molasses was five-fold diluted with methanol. The dilution was centrifuged at 21,400 x g for 15 minutes at room temperature to remove insoluble matter. The supernatant obtained was transferred into a 2-liter Erlenmeyer flask, to which isopropanol at a half volume was added portionwise with stirring. The flask was left at room temperature for a while until the resulting precipitate adhered to the wall of the flask. The supernatant was then discarded by decantation. To the precipitate was added 500 ml of ethanol, and the mixture was washed by stirring with a rotary shaker. The washing was further repeated several times. The washed precipitate was scraped off from the wall of the flask, followed by air drying on a filter paper. The air-dried precipitate (dry powder) was dissolved in purified water to about 40% (w/v). To this solution was added AG501-X8(D) of BioRad, followed by stirring. This operation was repeated until the color of the solution became almost unobserved. The resulting solution was treated with a Sep-Pak QMA column of Millipore, and further pretreated with Sep-Pak CM, Sep-Pak C18 and Sep-Pak Silica columns of Millipore. The resulting solution was loaded at a volume of 5 ml onto a column of Wako-gel LP40C18 (Wako Pure Chemical Industries, 2.6 cm x 85 cm), and eluted with purified water. The sugar content of the eluate was measured with a portable sugar refractometer, and the sugar composition was analyzed by high performance liquid chromatography (HPLC) with a Sugar-pak Na (7.8 mm x 300 mm) column of Millipore. The detection of sugars was carried out with model 410 Differential Refractometer of Waters. The eluate containing galactinol was lyophilized, and the resulting lyophilized powder was dissolved in 5 ml of purified water. The solution was loaded onto a column of TOYOPEARL HW40(S) (Toso, 2.6 cm x 90 cm), and eluted with purified water. The eluate was analyzed in the same manner as described above, so that purified galactinol was obtained.

The galactinol obtained was kept at 25°C for 40 minutes in the reaction mixture that came to contain 80 mM phosphate buffer (pH 6.5), 2 mg/ml galactinol, and 8.3 U α-galactosidase (Boehringer Mannheim, E. coli overproducer 662038). The reaction mixture was extracted with chloroform, and the water layer was analyzed by HPLC. The resulting galactinol was confirmed to be hydrolyzed into galactose and myo-inositol.

Example 2 (Measurement of Raffinose Synthase Activity)

The raffinose synthetase activity was measured under the following conditions according to the description of L. Lehle and W. Tanner, Eur. J. Biochem., 38, 103-110 (1973).

First, 2 µl of a sample to be used in the measurement of activity was added to 18 µl of the reaction mixture that came to contain 100 mM Tris-HCl (pH 7.4), 5 mM DTT (dithiothreitol), 0.01% BSA, 200 µM sucrose, 5 mM galactinol, 740 KBq/ml (31.7 µM) [¹⁴C] sucrose, and the reaction mixture was kept at 37°C for 3 to 20 hours. After the reaction, 30 µl of ethanol was added to the reaction mixture, followed by stirring and centrifugation at 15,000 rpm for 5 minutes. The supernatant was spotted at a volume of 5 µl on an HPTLC plate of cellulose for thin layer chromatography (Merck, 10 cm x 20 cm), and developed with n-butanol : pyridine : water : acetic acid = 60 : 40 : 30 : 3. The developed plate was dried and then quantitatively analyzed with an imaging analyzer (Fuji Photographic Film, FUJIX Bio Imaging Analyzer BAS-2000II) for the determination of [¹⁴C] raffinose produced.

Example 3 (Purification of Raffinose Synthase)

The purification of raffinose synthetase from broad bean was carried out as follows: For each purified protein solution, proteins present in the protein solution were analyzed by SDS-PAGE (Daiichi Kagaku Yakuhin), and the enzyme activity thereof was measured according to the method described in Example 2.

First, 300 g of immature seeds of broad bean (Nintoku Issun) stored at -80°C was thawed and then peeled. The peeled seeds were put in 600 ml of 100 mM Tris-HCl (pH 7.4), 5 mM DTT (dithiothreitol), 1 mM EDTA, 1 mM PMSF (phenylmethylsulfonyl fluoride) and 1 mM benzamide, and ground on ice with a mortar. The ground material was centrifuged at 21,400 x g for 50 minutes at 4°C. To the resulting supernatant was added 10% polyethylene imine (pH 8.0) at a 1/20 volume. The mixture was stirred at 4°C for 15 minutes, and centrifuged at 15,700 x g for 20 minutes at 4°C. To the resulting supernatant was added 196 g/l of (NH₄)₂SO₄ with stirring. The mixture was stirred in ice for 30 minutes, and centrifuged at 15,700 x g for 20 minutes at 4°C. To the resulting supernatant was further added 142 g/l of (NH₄)₂SO₄ with stirring. After the stirring in ice for 30 minutes, the mixture was centrifuged at 15,700 x g for 20 minutes at 4°C. The resulting precipitate was dissolved in 50 ml of 100 mM Tris-HCl (pH 7.4) and 5 mM DTT (dithiothreitol), and the solution was dialyzed against 20 mM Tris-HCl (pH 7.4), 1 mM DTT (dithiothreitol) and 1 mM EDTA at 4°C overnight. After the dialysis, the suspension was centrifuged at 70,000 x g for 60 minutes at 4°C. To the resulting supernatant was added 1 mM benzamidine · HCl, 5 mM ε-amino-n-caproic acid, 1 µg/ml antipain, 1 µg/ml leupeptin and 10 mM EGTA, and 2 M KCl was further added portionwise at a 1/40 volume. The mixture was loaded onto a column of DEAE-Sephacel (Pharmacia, 2.5 cm x 21.5 cm) equilibrated with 0.05 M KCl, 20 mM Tris-HCl (pH 7.4), 1 mM DTT (dithiothreitol) and 1 mM EDTA, and the adsorbed proteins were eluted with a gradient of 0.05 to 0.5 M KCl. The purification steps up to this stage were repeated three times, and fractions having raffinose synthase activity were combined and then purified as follows:

To the eluted fraction having raffinose synthetase activity was added portionwise saturated (NH₄)₂SO₄ at a 1/4 volume. The solution was loaded onto a column of Phenyl-Sepharose (Pharmacia, 2.5 cm x 10.2 cm) equilibrated with 20% saturated (NH₄)₂SO₄, 20 mM Tris-HCl (pH 7.4), 1 mM DTT (dithiothreitol) and 1 mM EDTA, and the adsorbed proteins were eluted with a gradient of 20% to 0% (NH₄)₂SO₄. The resulting active fraction was diluted by the addition of 0.01 M potassium phosphate buffer (pH 7.5) at a 2-fold volume. The diluted solution was loaded onto a column of Econo-Pac 10DG (BioRad, 5 ml) previously equilibrated with 0.01 M potassium phosphate buffer (pH 7.5) and 2 mM DTT (dithiothreitol), and the adsorbed proteins were eluted with a gradient of 0.01 to 0.5 M potassium phosphate buffer (pH 7.5) and 2 mM DTT (dithiothreitol). The active fraction obtained at this stage was found to have been purified up to 6500-fold or higher specific activity. Part of the resulting purified protein solution having raffinose synthetase activity was loaded onto a column of Superdex 200 (Pharmacia, 1.6 cm x 60 cm) equilibrated with 0.2 M KCl, 20 mM Tris-HCl (pH 7.4), 1 mM DTT (dithiothreitol) and 1 mM EDTA. The purified proteins thus separated were subjected to SDS-PAGE, and the raffinose synthetase activity was measured. A protein band having raffinose synthetase activity was identified as having a molecular weight of about 90 kDa on the SDS-PAGE.

Example 4 (Analysis of Partial Amino Acid Sequence of Raffinose Synthase)

To about 1 ml of the purified protein solution, which had been purified with a column of Econo-Pac 10DG (BioRad, 5 ml) in Example 3, was added 100% TCA at a 1/9 volume, and the mixture was left on ice for 30 minutes. After centrifugation at 10,000 x g for 15 minutes, the resulting precipitate was suspended in 500 µl of cold acetone (-20°C), followed by further centrifugation. This acetone washing was repeated, and the collected precipitate was dried and then dissolved in 200 µl of SDS-sample buffer, followed by SDS-PAGE. CBB staining was effected for the electrophoresed gel, from which the band of a raffinose synthetase protein was cut out.

To the gel thus taken was added 1 ml of 50% acetonitrile and 0.2 M ammonium carbonate (pH 8.9), and washing was continued with stirring at room temperature for 20 minutes. The gel was washed once again in the same manner, and dried under reduced pressure to an extent giving a volume reduction. To this gel was 1 ml of 0.02% Tween-20 and 0.2 M ammonium carbonate (pH 8.9), and the mixture was stirred at room temperature for 15 minutes. After removal of the solution, 400 µl of 8 M urea and 0.4 M NH₄HCO₃ was added, to which 40 µl of 45 mM DTT (dithiothreitol) was further added, and the mixture was left at 50°C for 20 minutes. After complete return to room temperature, 4 µl of 1 M iodoacetic acid was added, and the mixture was stirred in the dark at room temperature for 20 minutes. After removal of the solution, 1 ml of purified water was added, and the mixture was stirred at room temperature for 5 minutes, followed by washing. After further two washings, 1 ml of 50% acetonitrile and 0.2 M ammonium carbonate (pH 8.9) was added, and the mixture was stirred at room temperature for 15 minutes. The same treatment was repeated once again, after which the solution was removed, and the gel was dried under reduced pressure to an extent giving a volume reduction.

To this gel was added a solution of Achromobacter Protease I (Takara, Residue-specific Protease Kit) at a volume of 100 µl. Further added was 0.02% Tween-20 and 0.2 M ammonium carbonate (pH 8.9) to an extent that the gel was not exposed from the surface of the solution, and the mixture was left at 37°C for 42 hours. Further added was 500 µl of 0.09% TFA and 70% acetonitrile, and the mixture was stirred at room temperature for 30 minutes. The resulting mixture as contained in a sample tube was floated in an ultrasonic bath, followed by ultrasonic treatment (BRANSON, 60 W output power) for 5 minutes. The tube and contents thus treated were centrifuged, and the resulting extract was collected in another silicone-coated sample tube. On the other hand, 500 µl of 0.09% TFA and 70% acetonitrile was added again to the precipitate, followed by repeated extraction in the same manner as described above. The resulting extracts were combined and then concentrated under reduced pressure to an extent giving a solution remained at a volume of 200 to 300 µl. To the concentrate was added 25 µl of 8 M urea and 0.4 M NH₄HCO₃, and the mixture was concentrated to an extent giving a solution remained at a volume of 100 µl or lower. The concentrate was brought to about 100 µl with purified water, and the mixture was filtered through a filter of Ultrafree C3 GV (Millipore). The filtrate obtained was then subjected to elution through a column of Aquapore BU-300 C-4 (2.1 mm x 300 mm) by a gradient of 0.1% TFA/2.1% to 68.6% acetonitrile. Absorbance at 215 nm was monitored to collect a fraction at a peak thereof. The sample collected was evaporated under reduced pressure to complete dryness, and then analyzed with a Protein Sequencer 473A of ABI to determine a partial amino acid sequence of a raffinose synthetase.

Example 5 (Preparation of cDNA)

About 2 g of immature seeds of broad bean (Nintoku Issun) was frozen in liquid nitrogen and then ground with a mortar, to which 20 ml of Isogen (Nippon Gene) was added, and the mixture was further thoroughly ground. The ground material was transferred into a centrifugation tube, to which 4 ml of chloroform was added, and the mixture was stirred with a vortex mixer and then centrifuged at 6,500 x g for 10 minutes at 4°C. The water layer was collected, to which 10 ml of isopropanol was added, and the mixture was stirred and then centrifuged at 6,500 x g for 10 minutes at 4°C. The resulting precipitate was washed with 10 ml of 70% ethanol and then dissolved in 1 ml of elution buffer (10 mM Tris-HCl (pH 7.5), 1 mM EDTA, 0.1% SDS). The solution was left at 60°C for 10 minutes and then centrifuged at 10,000 x g for 1 minute to remove insoluble matter. To the resulting supernatant was added an equivalent volume of Oligotex-dT30 (Takara), and the mixture was stirred and then left at 65°C for 5 minutes. The mixture was placed on ice and then left for 3 minutes, to which 200 µl of 5 M NaCl was added, and the mixture was left at 37°C for 10 minutes. The mixture was then centrifuged at 10,000 x g at 4°C for 3 minutes. The precipitate was collected and then suspended in 1 ml of TE buffer, and the suspension was left at 65°C for 5 minutes, which was placed on ice and then left for 3 minutes, followed by centrifugation at 10,000 x g for 3 minutes at 4°C to remove the precipitate.

To the resulting supernatant were added 100 µl of 3 M sodium acetate and 2 ml of ethanol, and RNA was ethanol precipitated and collected. The collected RNA was washed twice with 70% ethanol and then dissolved in 20 µl of sterilized water, which was used for the subsequent cDNA synthesis. The amount of RNA obtained was determined by the measurement of absorbance at 260 nm.

For the cDNA synthesis, First Strand Synthesis Kit for RT-PCR (Amercham) and cDNA Synthesis Kit (Takara) were used, and all operations were made according to the protocol.

Example 6 (Nucleotide sequence Analysis of Raffinose Synthase Gene from cDNA)

Based on the amino acid sequence obtained in Example 4, mixed synthetic DNA primers having the nucleotide sequences shown in list 5 below were synthesized. The PCR method was carried out with Gene Amp PCR Systems 2400 and DNA Thermal Cycler Model 480 of Perkin-Elmer using Advantage KlenTaq cDNA Kit of Clontech. The polymerase chain reaction was effected with the above primers at 94°C for 1 minute, at 50°C for 3 minutes, and at 72°C for 3 minutes, and this reaction was repeated forty times. As a result, the combinations of primers 8.2 and 13.3RV, primers 13.4 and 10.3RV, and primers 7.4 and 10.3RV, having the nucleotide sequences shown in list 5 below, gave an amplification of 1.2 kb, 0.5 kb, and 1.2 kb bands, respectively. These amplified DNA fragments were cloned with a TA cloning kit (Invitrogen), followed by sequence reaction using ABI PRISM Dye Terminator Cycle Sequencing Ready Reaction Kit of Perkin-Elmer and nucleotide sequence analysis with a 373S DNA sequencer of ABI. As a result, these DNA fragments were found to have a nucleotide sequence extending from base 813 to base 1915, base 1936 to base 2413, and base 1226 to base 2413, respectively, in the nucleotide sequence of SEQ ID NO:2. Based on these nucleotide sequences, synthetic DNA primers having nucleotide sequences shown in list 6 below were prepared, and the nucleotide sequences in both terminal regions of cDNA were analyzed with Marathon cDNA Amplification Kit of Clontech. As a result, the nucleotide sequence of SEQ ID NO:2 was finally determined.

(List 5)

#8.2

26mer

AA(AG) AC(ATGC) GC(ATGC) CC(ATGC) AG(TC) AT(TCA) AT(TCA) GAC AA

#13.4

20mer

AA(AG) AT(TCA) TGG AA(TC) CT(ATGC) AAC AA

#7.4

24mer

AA(AG) GC(ATGC) AG(AG) GT(ATGC) GT(ATGC) GT(ATGC) CC(ATGC) AAG

#13.3RV

21mer

(TC)TT (AG)TT (ATGC)AG (AG)TT CCA (AGT)AT TTT

#10.3RV

21mer

(TC)TT (AG)TC (TC)TC (AG)TA (ATGC)AG (AG)AA TTT

(List 6)

RS-2RV

30mer

GGCTGAGGTTCGGTTCATTCCTGAATCATC

RS-7

30mer

CCAAATGGTACATATTGGCTCCAAGGTTGT

RS-8

30mer

AAGAGTGTATCTGAATTTTCACGCGCGGTG

RS-9

30mer

TGGTGCAATGGGAAAACTCCAATGAGCACC

RS-10

30mer

ATGAAGTGTTCTGATAGATTGAAAGTTTCG

RS-11

30mer

CAGTCTCTGGAGTTTGATGATAATGCAAGT

Example 7 (Cloning of Raffinose Synthetase Gene from Broad Bean cDNA)

The primers designed from the amino acid sequence of SEQ ID NO:1, i.e., primers having nucleotide sequences shown in list 7 below, were synthesized. Using these primers and cDNA obtained in Example 5 as a template, a DNA fragment of the open reading frame region was amplified by PCR under the conditions described in Example 6. The amplified DNA fragment was digested with the restriction endonucleases Bam HI and Xba I whose recognition sequences were contained in the primers used. Using Ligation Kit (Takara), the DNA fragment thus digested was cloned in the plasmid pBluescriptII KS- (Stratagene) previously digested with Bam HI and Xba I. The nucleotide sequence of the cloned DNA fragment was confirmed with ABI PRISM Dye Terminator Cycle Sequencing Ready Reaction Kit of Perkin-Elmer. In the clone thus obtained, it was found that the base at position 1591 in the nucleotide sequence of SEQ ID NO:2 had been changed from thymine (T) to cytosine (C). This was, however, a nonsense mutation without a change of the amino acid; therefore, this clone was designated pBluescriptKS-RS, and used in the subsequent experiment.

(List 7)

RS-N

41mer

CGCGGATCCACCATGGCACCACCAAGCATAACCAAAACTGC

RS-C

37mer

TGCTCTAGATTATCAAAATAAAAACTGGACCAAAGAC

Example 8 (Expression of Broad Bean Raffinose Synthetase Gene in E. coli)

The plasmid pBluescriptKS-RS having the broad bean raffinose synthetase gene obtained in Example 7 was digested with Bam HI and Not I, and cloned in the plasmid pGEX-4T3 (Pharmacia) digested with Bam HI and Not I to give the plasmid pGEX-RS as shown in Figure 1.

The plasmid pBluescriptKS-RS was digested with Nco I and Xba I, and cloned in the plasmid pTrc99A (Pharmacia) digested with Nco I and Xba I to give the plasmid pTrc-RS as shown in Figure 1.

These plasmids were introduced into E. coli strain HB101, and the resulting transformants were used for the confirmation of raffinose synthetase expression. Overnight cultures of the transformants were inoculated at a volume of 1 ml each into 100 ml of LB medium and incubated at 37°C for about 3 hours, followed by the addition of IPTG (isopropylthio-β-D-galactoside) to a final concentration of 1 mM and further incubation for 5 hours. The cultures were centrifuged at 21,400 x g for 10 minutes, and the bacterial cells were collected. The collected bacterial cells were stored at -80°C. To the frozen bacterial cells was added a 10-fold volume of 100 mM Tris-HCl (pH 7.4), 1 mM EDTA, 5 mM DTT (dithiothreitol), 1 mM PMSF (phenylmethylsulfonyl fluoride) and 1 mM benzamide, and the bacterial cells were thawed and suspended. These suspensions were treated with an ultrasonic disrupter (Branson) to effect the disruption of the bacterial cells. The disrupted cell mixtures obtained were centrifuged at 16,000 x g for 10 minutes, and soluble protein solutions were collected.

The protein solutions thus obtained were used at a volume of 4 µl each for the measurement of raffinose synthetase activity according to the method described above. The reaction was effected at 37°C for 64 hours. As a control, E. coli strain HB101 that had been transformed with one of the vectors, pGEX-4T3, was used. The results are shown in Table 1. The synthesis of raffinose was detected in the samples from the transformants HB101 (pGEX-RS) and HB101 (pTrc-RS).

Transformant

Amount of raffinose produced (pmol)

HB101 (pGEX4T-3)

0.56

HB101 (pGEX-RS)

10.50

HB101 (pTrc-RS)

11.10

Example 9 (Cloning of Raffinose Synthetase Gene from Soybean cDNA)

In the same manner as described in Example 5, cDNA was obtained from immature seeds of soybean (Glycine max) Williams 82. Using this cDNA as a template and primers designed from the amino acid sequence of SEQ ID NO:1, i.e., primers having nucleotide sequences shown in list 8 below, a DNA fragment was amplified by PCR under the conditions described in Example 6. The DNA fragment thus amplified by PCR was cloned with a TA cloning kit (Invitrogen), followed by sequence reaction using ABI PRISM Dye Terminator Cycle Sequencing Ready Reaction Kit of Perkin-Elmer and nucleotide sequence analysis with a 373S DNA sequencer of ABI. Based on this sequence, primers having nucleotide sequences shown in list 9 below were synthesized. The synthesis of cDNA was carried out with Marathon Kit of Clontech using mRNA obtained in the same manner as described in Example 5 from leaves of soybean Williams 82. The cDNA obtained was ligated to an adaptor contained in this kit with ligase. This operation was made according to the protocol attached. Using the adaptor-ligated cDNA thus prepared, polymerase chain reaction was effected with the primers shown in list 9 below. The nucleotide sequences in both terminal regions of the gene were analyzed according to the protocol attached to the Marathon Kit of Clontech. As a result, the nucleotide sequence of SEQ ID NO:4 was determined.

(List 8)

1-F primer

35mer

CGATTIAAIGTITGGTGGACIACICAITGGGTIGG

2-RV primer

45mer

GGCCTAIAAIGCITCCCAIGTICACCAICCIAAITTITCIATIAT

5-F primer

41mer

CGATGGATGGGIAAITTIATICAICCIGAITGGGAIATGTT

6-RV primer

32mer

GGCCACATITTIACIA(AG)ICCIATIGGIGCIAA

(List 9)

SN-1

30mer

CACGAACTGGGGCACGAGACACAGATGATG

SC-3RV

30mer

AAGCAAGTCACGGAGTGTGAATAGTCAGAG

SC-5

30mer

ACACGAGACTGTTTGTTTGAAGACCCCTTG

SC-6

25mer

TGGAATCTCAACAAATATACAGGTG

SN-3RV

30mer

GGGTCATGGCCAACGTGGACGTATAAGCAC

SN-4RV

30mer

GATGATCACTGGCGCGGTTTTCTCCTCGAG

Example 10 (Acquisition of Raffinose Synthetase Gene from Japanese Artichoke cDNA)

In the same manner as described in Example 5, cDNA was obtained from leaves of Japanese artichoke (Stachys sieboldii). Using this cDNA as a template and primers designed from the amino acid sequence of SEQ ID NO:1, i.e., primers having nucleotide sequences shown in list 10 below, a DNA fragment was amplified by PCR under the conditions described in Example 6. The DNA fragment thus amplified by PCR was cloned with a TA cloning kit (Invitrogen), followed by sequence reaction using ABI PRISM Dye Terminator Cycle Sequencing Ready Reaction Kit of Perkin-Elmer and nucleotide sequence analysis with a 373S DNA sequencer of ABI. As a result, the nucleotide sequence of SEQ ID:6 was determined.

Based on the nucleotide sequence thus obtained, synthesized DNA primers are prepared, and in the same manner as described in Example 9, the nucleotide sequences in both terminal regions of the gene are analyzed with Marathon Kit of Clontech.

(List 10)

1-F primer

35mer

CGATTIAAIGTITGGTGGACIACICAITGGGTIGG

4-RV primer

37mer

GGCCAGCIATIACICCITTICCITTIAAITGITTITT

2-F primer

44mer

CGAATIATIGAIAAITTIGGITGGTGIACITGGGAIGCITTITA

6-RV primer

32mer

GGCCACATITTIACIA(AG)ICCIATIGGIGCIAA

Example 11 (Acquisition of Raffinose Synthetase Gene from Corn cDNA)

In the same manner as described in Example 5, cDNA was obtained from leaves of corn (Zea mays L.) Pioneer 3358. Using this cDNA as a template and primers designed from the amino acid sequence of SEQ ID NO:1, i.e., primers having nucleotide sequences shown in list 11 below, a DNA fragment was amplified by PCR under the conditions described in Example 6. The DNA fragment thus amplified by PCR was cloned with a TA cloning kit (Invitrogen), followed by sequence reaction using ABI PRISM Dye Terminator Cycle Sequencing Ready Reaction Kit of Perkin-Elmer and nucleotide sequence analysis with a 373S DNA sequencer of ABI. Based on this sequence, primers having nucleotide sequences shown in list 12 below were synthesized. In the same manner as described in Example 5, mRNA obtained from leaves of corn (Zea mays L.) Pioneer 3358 was linked to an adaptor contained in the Marathon Kit of Clontech with ligase. This operation was made according to the protocol attached. Using the adaptor-ligated cDNA thus prepared, polymerase chain reaction was effected in the same manner as described above with the primers shown in list 12 below. As a result, the nucleotide sequence of SEQ ID NO:8 was determined.

Based on the nucleotide sequence thus obtained, synthesized DNA primers are prepared, and in the same manner as described in Example 9, the nucleotide sequence in the 5'-terminal region of the gene is analyzed with Marathon Kit of Clontech.

(List 11)

5-F primer

41mer

CGATGGATGGGIAAITTIATICAICCIGAITGGGAIATGTT

6-RV primer

32mer

GGCCACATITTIACIA(AG)ICCIATIGGIGCIAA

(List 12)

M-10 primer

25mer

GACGTCGAGTGGAAGAGCGGCAAGG

M-11 primer

25mer

CACCTACGAGCTCTTCGTCGTTGCC

Example 12 (Construction of Expression Vectors in Plant for Chimera Gene, 35S-Broad Bean Raffinose Synthetase Gene)

The plasmid pBluescriptKS-RS having the broad bean raffinose synthetase gene obtained in Example 7 was digested with the restriction endonucleases Bam HI and Sac I. Using Ligation Kit (Takara), the DNA fragment thus digested was cloned in the binary vector pBI121 (Clontech) previously digested with Bam HI and Sac I. The vector thus obtained was designated pBI121-RS.

For an antisense experiment, plasmid pBI121 (Clontech) previously digested with Bam HI and Sac I was ligated to linkers shown in list 13 below to give pBI121(-). This pBI121(-) was used to prepare pBI121(-)-RS in the same manner as described for the preparation of pBI121-RS above.

A similar vector was prepared with pBI221. The plasmid pBluescriptKS-RS obtained in Example 7 was digested with the restriction endonucleases Bam HI and Sac I. Using Ligation Kit (Takara), the DNA fragment thus digested was cloned in the vector pBI221 (Clontech) previously digested with Bam HI and Sac I. The vector thus obtained was designated pBI221-RS.

For an antisense experiment, plasmid pBI221 (Clontech) previously digested with Bam HI and Sac I was ligated to linkers shown in list 13 below to give pBI221(-). This pBI221(-) was used to prepare pBI221(-)-RS in the same manner as described for the preparation of pBI221-RS above.

The construction of these expression vectors is shown in Figures 2 and 3.

(List 13)

BamSac-(+) linker

25mer

GATCGAGCTCGTGTCGGATCCAGCT

BamSac-(-) linker

17mer

GGATCCGACACGAGCTC

Example 13 (Transformation of Mustard with Broad Bean Raffinose Synthetase Gene)

The vectors pBI121-RS and pBI121(-)-RS prepared in Example 12 were used for the transformation of mustard (Brassica juncia) by the Agrobacterium infection method.

Agrobacterium tumefaciens (strain C58C1, rifampicin resistant) previously made into a competent state by calcium chloride treatment was transformed independently with two plasmids pBI121-RS and pBI121(-)-RS prepared in Example 12. Selection for transformants was carried out on LB medium containing 50 µg/ml rifampicin and 25 µg/ml kanamycin by utilizing the character of kanamycin resistance conferred by the kanamycin resistance gene (neomycin phosphotransferase, NPTII) of the introduced plasmids.

The transformant Agrobacterium obtained (Agrobacterium tumefaciens strain C58, rifampicin resistant) was cultivated on LB medium containing 50 µg/ml rifampicin and 25 µg/ml kanamycin at 28°C for a whole day and night, and the culture was used for the transformation of mustard by the method described below.

The seeds of mustard were aseptically sowed on 1/2 MS medium, 2% sucrose, 0.7% agar. After one week, cotyledons and petioles of sprouting plants were cut out with a scalpel, and transferred to MS medium, 3% sucrose, 0.7% agar, 4.5 µM BA, 0.05 µM 2.4-D, 3.3 µM AgNO₃, followed by precultivation for 1 day. The precultivated cotyledons and petioles were transferred in a 1000-fold dilution of the Agrobacterium culture to cause infection for 5 minutes. The infected cotyledons and petioles were transferred again to the same medium as used in the precultivation, and cultivated for 3 to 4 days. The cultivated cotyledons and petioles were transferred to MS medium, 3% sucrose, 4.5 µM BA, 0.05 µM 2.4-D, 3.3 µM AgNO₃, 500 mg/l cefotaxim, and sterilized with shaking for 1 day. The sterilized cotyledons and petioles were transferred to MS medium, 3% sucrose, 0.7% agar, 4.5 µM BA, 0.05 µM 2.4-D, 3.3 µM AgNO₃, 100 mg/l cefotaxim, 20 mg/l kanamycin, and cultivated for 3 to 4 weeks. The cotyledons and petioles were transferred to MS medium, 3% sucrose, 0.7% agar, 4.5 µM BA, 0.05 µM 2.4-D, 100 mg/l cefotaxim, 20 mg/l kanamycin, and cultivated. The cultivation on this medium was continued with subculturing at intervals of 3 to 4 weeks. When the regeneration of shoots began to occur, these shoots were subcultured on MS medium, 3% sucrose, 0.7% agar, 20 mg/l kanamycin, and cultivated for 3 to 4 weeks. The rooting plants were transferred to vermiculite : peat moss = 1 : 1, and conditioned at 21° to 22°C in a cycle of day/night = 12 hours : 12 hours. With the progress of plant body growth, the plants were suitably grown with cultivation soil. From leaves of the regenerated plants, genomic DNA was extracted according to the method described above, and the gene insertion into the plant genome was confirmed by PCR using the primers shown in list 14 below.

(List 14)

35S

30mer

TTCCAGTATGGACGATTCAAGGCTTGCTTC

NOS

25mer

ATGTATAATTGCGGGACTCTAATCA

RS-F

30mer

AAGAGTGTATCTGAATTTTCACGCGCGGTG

RS-RV

33mer

ACCTTCCCATACACCTTTTGGATGAACCTTCAA

Example 14 (Transformation of Soybean Somatic Embryo with Broad Bean Raffinose Synthetase Gene)

Cultured cells of soybean "Fayette" somatic embryos (400 to 500 mg FW) were arranged in one layer within a circle having a diameter of 20 mm on the central part of a 6 cm agar plate. Two plasmids pBI221-RS and pBI221(-)-RS having chimera genes prepared from the broad bean raffinose synthetase gene and 35S promoter in Example 12 were introduced into the soybean somatic embryos according to the disclosure of the Japanese Patent Application No. 3-291501/1991. That is, these plasmids were mixed with the β-glucuronidase (GUS)/hygromycin-resistant gene (HPT) coexpression vector pSUM-GH:NotI for selection described in Soshiki Baiyo, 20, 323-327 (1994). These mixed plasmids were used for the gene introduction into the soybean somatic embryos with a particle gun (800 mg/coating gold particles 200 µg/shot; projectile stopper-sample distance, 100 mm). After the introduction, gyratory cultures were grown in the MS modified growth liquid medium (Sigma) containing 25 to 50 µg/ml hygromycin under illumination at 25°C for 16 hours, and transformed somatic embryos were selected.

For the hygromycin-resistant soybean somatic embryos having yellowish green color and growth ability, which were selected after about 3 months, polymerization chain reaction is effected with primers shown in list 14 above to determine whether the broad bean raffinose synthetase gene region is amplified or not. This confirms that the broad bean raffinose synthetase gene is inserted into the soybean genome.

Furthermore, the somatic embryos obtained are used for the regeneration of plants to give transformant soybean with the broad bean raffinose synthetase gene.

Medium Composition

LB and MS media used in the above Examples have the following respective compositions.

(LB medium)

Bacto-tryptone

10 g

Bacto-yeast extract

5 g

NaCl

10 g / 1 liter H₂O (pH 7.0)

(MS medium)

KNO₃

2022 mg/l

NH₄NO₃

1650 mg/l

NH₄Cl

2140 mg/l

KH₂PO₄

170 mg/l

MgSO₄ · 7H₂O

370 mg/l

CaCl₂ · 2H₂O

440 mg/l

MnSO₄ · 4H₂O

22.3 mg/l

ZnSO₄ · 7H₂O

8.6 mg/l

CuSO₄ · 5H₂O

0.025 mg/l

KI

0.83 mg/l

CoCl₂ · 6H₂O

0.025 mg/l

H₃BO₃

6.2 mg/l

NaMoO4 · 2H₂O

0.25 mg/l

FeSO₄ · 7H₂O

27.8 mg/l

Na₂EDTA

37.3 mg/l

Nicotinic acid

0.5 mg/l

Thiamine HCl

1 mg/l

Pyridoxine HCl

0.5 mg/l

Inositol

100 mg/l

Glycine

2 mg/l

Brief Description of the Sequences

1. SEQ ID NO:1:

The sequence of SEQ ID NO:1 shows an amino acid sequence of a raffinose synthetase protein encoded in the raffinose synthetase gene obtained from broad bean.

2. SEQ ID NO:2:

The sequence of SEQ ID NO:2 shows a cDNA nucleotide sequence of the raffinose synthetase gene obtained from broad bean.

3. SEQ ID NO:3:

The sequence of SEQ ID NO:3 shows an amino acid sequence of a raffinose synthetase protein encoded in the raffinose synthetase gene obtained from soybean.

4. SEQ ID NO:4:

The sequence of SEQ ID NO:4 shows a cDNA nucleotide sequence of the raffinose synthetase gene obtained from soybean.

5. SEQ ID NO:5:

The sequence of SEQ ID NO:5 shows an amino acid sequence of a raffinose synthetase protein encoded in the raffinose synthetase gene obtained from Japanese artichoke.

6. SEQ ID NO:6:

The sequence of SEQ ID NO:6 shows a cDNA nucleotide sequence of the raffinose synthetase gene obtained from Japanese artichoke.

7. SEQ ID NO:7:

The sequence of SEQ ID NO:7 shows an amino acid sequence of a raffinose synthetase protein encoded in the raffinose synthetase gene obtained from corn.

8. SEQ ID NO:8:

The sequence of SEQ ID NO:8 shows a cDNA nucleotide sequence of the raffinose synthetase gene obtained from corn.

9. List 1:

The nucleotide sequences shown in list 1 are of the typical primers used in the amplification of a cDNA fragment of a raffinose synthetase gene. All of these sequences are based on the nucleotide sequence in the non-coding region of the gene. Primer 1 is a sense primer corresponding to the 5'-terminus of a cDNA fragment of the broad bean-derived raffinose synthetase gene. Primers 2 and 3 are antisense primers corresponding to the 3'-terminus of the cDNA fragment of the broad bean-derived raffinose synthetase gene. Primer 4 is a sense primer corresponding to the 5'-terminus of a cDNA fragment of the soybean-derived raffinose synthetase gene. Primers 5 and 6 are antisense primers corresponding to the 3'-terminus of the cDNA fragment of the soybean-derived raffinose synthetase gene. Depending upon the purpose, recognition sequences for suitable restriction endonucleases can be added to the 5'-termini of these nucleotide sequences in an appropriate manner.

10. List 2:

The nucleotide sequences shown in list 2 are of the typical primers used in the amplification of an open reading frame coding for the amino acid sequence of a raffinose synthetase protein in the cDNA sequence of a raffinose synthetase gene. Primers 1 and 2 are sense primers corresponding to the N-terminus of the broad bean-derived raffinose synthetase protein. Primers 3 and 4 are antisense primers corresponding to the C-terminus of the broad bean-derived raffinose synthetase protein. Primers 5 and 6 are sense primers corresponding to the N-terminus of the soybean-derived raffinose synthetase protein. Primers 7 and 8 are antisense primers corresponding to the C-terminus of the soybean-derived raffinose synthetase protein. Depending upon the purpose, recognition sequences for suitable restriction endonucleases can be added to the 5'-termini of these sequences in an appropriate manner.

11. List 3:

The amino acid sequences shown in list 3 are partial amino acid sequences of a raffinose synthetase protein.

• #1 is equivalent to the partial amino acid sequence extending from amino acid 110 to amino acid 129 in the amino acid sequence of SEQ ID NO:1.
• #2 is equivalent to the partial amino acid sequence extending from amino acid 234 to amino acid 247 in the amino acid sequence of SEQ ID NO:1.
• #3 is equivalent to the partial amino acid sequence extending from amino acid 265 to amino acid 279 in the amino acid sequence of SEQ ID NO:1.
• #4 is equivalent to the partial amino acid sequence extending from amino acid 296 to amino acid 312 in the amino acid sequence of SEQ ID NO:1.
• #5 is equivalent to the partial amino acid sequence extending from amino acid 346 to amino acid 361 in the amino acid sequence of SEQ ID NO:1.
• #6 is equivalent to the partial amino acid sequence extending from amino acid 383 to amino acid 402 in the amino acid sequence of SEQ ID NO:1.
• #7 is equivalent to the partial amino acid sequence extending from amino acid 411 to amino acid 433 in the amino acid sequence of SEQ ID NO:1.
• #8 is equivalent to the partial amino acid sequence extending from amino acid 440 to amino acid 453 in the amino acid sequence of SEQ ID NO:1.
• #9 is equivalent to the partial amino acid sequence extending from amino acid 457 to amino acid 468 in the amino acid sequence of SEQ ID NO:1.
• #10 is equivalent to the partial amino acid sequence extending from amino acid 471 to amino acid 516 in the amino acid sequence of SEQ ID NO:1.
• #11 is equivalent to the partial amino acid sequence extending from amino acid 517 to amino acid 559 in the amino acid sequence of SEQ ID NO:1.
• #12 is equivalent to the partial amino acid sequence extending from amino acid 574 to amino acid 582 in the amino acid sequence of SEQ ID NO:1.
• #13 is equivalent to the partial amino acid sequence extending from amino acid 586 to amino acid 609 in the amino acid sequence of SEQ ID NO:1.
• #14 is equivalent to the partial amino acid sequence extending from amino acid 615 to amino acid 627 in the amino acid sequence of SEQ ID NO:1.
• #15 is equivalent to the partial amino acid sequence extending from amino acid 716 to amino acid 724 in the amino acid sequence of SEQ ID NO:1.

12. List 4:

The nucleotide sequences shown in list 4 are of the typical primers synthesized on some of the amino acid sequences shown in list 3. The symbol "F" as used after the primer number means that the primer referred to by this symbol has a sense sequence. The symbol "RV" as used after the primer number means that the primer referred to by this symbol has an antisense sequence. Primer 1 corresponds to the partial amino acid sequence extending from amino acid 119 to amino acid 129 in the amino acid sequence of SEQ ID NO:1. Primer 2 corresponds to the partial amino acid sequence extending from amino acid 234 to amino acid 247 in the amino acid sequence of SEQ ID NO:1. Primer 3 corresponds to the partial amino acid sequence extending from amino acid 265 to amino acid 279 in the amino acid sequence of SEQ ID NO:1. Primer 4 corresponds to the partial amino acid sequence extending from amino acid 458 to amino acid 468 in the amino acid sequence of SEQ ID NO:1. Primer 5 corresponds to the partial amino acid sequence extending from amino acid 522 to amino acid 534 in the amino acid sequence of SEQ ID NO:1. Primer 6 corresponds to the partial amino acid sequence extending from amino acid 716 to amino acid 724 in the amino acid sequence of SEQ ID NO:1.

13. List 5:

The nucleotide sequences shown in list 5 are of the typical primers synthesized on the partial amino acid sequences of the purified broad bean raffinose synthetase protein. The bases shown in parentheses mean that a mixture of those bases was used in the synthesis. The symbol "RV" as used after the primer number means that the primer referred to by this symbol has an antisense sequence.

14. List 6:

The nucleotide sequences shown in list 6 are of the typical primers used in the analysis of both terminal regions of a cDNA nucleotide sequence of the broad bean raffinose synthetase gene by the RACE method. The symbol "RV" as used after the primer number means that the primer referred to by this symbol has an antisense sequence.

15. List 7:

The nucleotide sequences shown in list 7 are of the typical primers used in the cloning of the broad bean raffinose synthetase gene. RS-N corresponds to the N-terminus of the open reading frame and contains two recognition sites for the restriction endonucleases Bam HI and Nco I on the 5'-terminal side. RS-C is an antisense primer corresponding to the C-terminus of the open reading frame and contains a recognition site for the restriction endonuclease Xba I on the 5'-terminal side.

16. List 8:

The nucleotide sequences shown in list 8 are of the typical primers used in the cloning of a soybean raffinose synthetase gene fragment. The base represented by the symbol "I" was inosine used in the synthesis. The symbol "RV" as used after the primer number means that the primer referred to by this symbol has an antisense sequence.

17. List 9:

The nucleotide sequences shown in list 9 are of the typical primers used in the analysis of the cDNA nucleotide sequence of a soybean raffinose synthetase gene fragment. The symbol "RV" as used after the primer number means that the primer referred to by this symbol has an antisense sequence.

The analysis of nucleotide sequences was carried out by polymerase chain reaction using SN-1 and SC-3RV. SC-5 and SC-6 were used in the analysis of a nucleotide sequence in the 3'-terminal region, and SN-3RV and SN-4RV were used in the analysis of a nucleotide sequence in the 5'-terminal region.

18. List 10:

The nucleotide sequences shown in list 10 are of the typical primers used in the analysis of the cDNA nucleotide sequence of a Japanese artichoke raffinose synthetase gene fragment. The base represented by the symbol "I" was inosine used in the synthesis. The symbol "RV" as used after the primer number means that the primer referred to by this symbol has an antisense sequence.

19. List 11:

The nucleotide sequences shown in list 11 are of the typical primers used in the analysis of the cDNA nucleotide sequence of a corn raffinose synthetase gene fragment. The base represented by the symbol "I" was inosine used in the synthesis. The symbol "RV" as used after the primer number means that the primer referred to by this symbol has an antisense sequence.

20. List 12:

The nucleotide sequences shown in list 12 are of the typical primers used in the analysis of the cDNA nucleotide sequence of a corn raffinose synthetase gene fragment. M-10 and M-11 were used in the analysis of a nucleotide sequence in the 3'-terminal region.

21. List 13:

The nucleotide sequences shown in list 13 are of the typical adopters used in the construction of vectors for antisense experiments. These synthetic DNA fragments takes a double-stranded form when mixed together because they are complementary strands. This double-stranded DNA fragment has cohesive ends of cleavage sites for the restriction endonucleases Bam HI and Sac I on both termini, and contains the restriction sites for the restriction endonucleases Bam HI and Sac I in the double-stranded region.

22. List 14:

The nucleotide sequences shown in list 14 are of the typical primers used in the PCR experiment to confirm the gene introduction into the genome of a recombinant plant. 35S is a primer toward the downstream region at the 35S promoter site, and NOS is a primer toward the upstream region at the NOS terminator site. RS-F is a sense primer of the broad bean raffinose synthetase gene, and RS-RV is an antisense primer of the broad bean raffinose synthetase gene.